#include <stdio.h>

int factorials[10] = {0};

int factorial(int n) {
    if (factorials[n-1] == 0) {
        factorials[n-1] = n * factorial(n-1);
    }
    return factorials[n-1];
}

int main() {
    int k = 0, sum = 0, i;
    scanf("%d", &k);
    factorials[0] = 1;
    for (i = 1;i <= k; i++) {
        sum += factorial(i);
    }
    printf("%d", sum);
    return 0;
}